INSTYTUT DENDROLOGII

Abstract: Laboratory experiments were made to determine the optimum conditions for dormancy breaking in the midland hawthorn (Crataegus laevigata (Poir.) DC. = C. oxyacantha L.). Its small applelike fruits should be collected when they are fully ripe (in Poland in October). The nutlets extracted from the fruits must be dried at room temperature to the moisture content of 9–13%. The dormancy of midland hawthorn seeds can be overcome by: (1) stratification in a moist medium: 20~30°C/3°C, 16–20 weeks at 20~30°C (16+8 hrs or 24+24 hrs) followed by 16–18 weeks at 3°C, i.e. to the time when first radicles start to appear; or (2) chemical scarification in concentrated sulphuric acid for 2 or 3 hrs, followed by warm stratification at 27.5°C or 20~30°C for 4 weeks and cold stratification at 3°C, lasting 19–21 weeks, i.e. to the time when first radicles start to appear. The stratified seeds germinate vigorously (in 3–5 weeks) and at a high percentage at temperatures of 3~15°C or 3~20°C (16+8 hrs) and all seedlings emerge in such conditions about 4–6 weeks after sowing. Seed germination after stratification or scarification can be stopped by partial desiccation of seeds. Seed desiccation after stratification to the moisture content of 10–13% and sealed storage at –3°C for one year do not reduce seed germination and seedling emergence rates of the previously pretreated seeds. Storage for 20 months at –3°C of seeds dried after harvest to the moisture content of 14% does not reduce their germination and seedling emergence.

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